Welcome to the forum.
The reason you are having trouble finding information probably is that accurate statistics really aren't available -- only the judgment of experts. But for a stand-alone antibody test, good estimateswith which most experts would agree) are around 50% positive by 2 weeks and 70-80% at 3 weeks.
But you don't need to wait 3 months for definitive testing. Despite common advice about 3 months, with the current, routinely used antibody tests, 6 weeks and certainly 8 weeks generally is sufficient time for a 100% reliable result. (In case you are interested why the 3 month advice persists, see the following threaad, in particular my follow-up comment dated Sept 18:
http://www.medhelp.org/posts/HIV-Prevention/-A-Question-on-Testing/show/1347755).
If you find a clinic or physician where the combo test (for both HIV antibody and p24 antigen) is offered, a negative result is 100% any time 4 weeks or more after the last possible exposure.
I hope this helps. Best wishes and stay safe-- HHH, MD